Pneumatic memory relay

ABSTRACT

A memory relay has a poppet movable between two positions in a space of the relay housing. The poppet surfaces are arranged to sealingly engage in each position a seat which bounds an input conduit arranged to receive a fluid under pressure. An output conduit is in communication with both the space and the exterior of the housing. Elements are provided for moving the poppet from one position to the other in response to the application of a set or reset signal to the relay whereby the pressure in one or in the other input conduit is caused to appear at the output conduit. A magnet arrangement is provided for retaining the poppet in at least one position independently of the presence or absence of the pressures in the input conduits.

United States Patent [191 Bouteille June 25, 1974 PNEUMATIC MEMORY RELAY[76] Inventor: Daniel Bouteille, 3 Rue Lanen, 'm l 92190 Meudon FranceASSZSHIHI Exammer-Robert Miller a Attorney, Agent, or Firm-Mwhael S.Striker [22] Filed: Aug. 16, 1972 [57] ABSTRACT A memory relay has apoppet movable between two positions in a space of the relay housing.The poppet [30] Foreign Application Priority Data l surfaces arearranged to sealmgly engage in each POSI- Aug. 18, 197! France 71.30746tion a Seat which bounds an input conduit arranged to rec at] 'd der e.t [52 US. Cl. l37/625.66, 235/201 ME P [51] Int Cl F16k 11/02 Fl6k31/385 606d 1/02 An output conduit 15 m communicatlon with both the a[58] Fieid 'f' /625 6 625 27 space and the exterior of the housing.Elements are 137/608. 1/ provided for moving the poppet from oneposition to 331 1 the other in response to the application of a set orreset signal to the relay whereby the pressure in one or [56] ReferencesCited in the other input conduit is caused to appear at the t outputconduit. A magnet arrangement is provided for UNITED STATES PATENTSretaining the poppet in at least one position 52325333 21132; 52525155;Iii/ 5222 5 t, 3* the 7 Q t t t 3,559,945 2/I97l Coiner 235/201 MEpressures 6 con m 3,601,155 8/1971 Brown l. l37/625.66 23 Claims, 4Drawing Figures 2 l3 9 I6 I I l X 1 i I I i P --4 F L E I p 5 E 2 z;

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l PNEUMATIC MEMORY RELAY BACKGROUND OF THE INVENTION The presentinvention relates to a pneumatic control device for automatic systems,and more particularly to pneumatic relays which can be controlled bypneumatic pulses and which have a memory or operate as a flip-flop, i.e.they retain the state set by a control pulse even after the pulse hasdisappeared.

It is often required in industrial applications to utilize a pneumaticrelay which operates as a flip-flop, i.e. can be alternatingly set toone of two stable states by pneumatic control pulses. Various types ofsuchrelays are already known. Most of the known relays are of the spoolvalve type, wherein the fluid switching is achievedby the movement of aspool that slides under the action of control pressures which areapplied at its ends. After the control pressures have-disappeared, thespool canbe maintained in the position set by the control pressurepulse, by the inherent friction present in the structure, i.e., thefriction between the seals needed to seal the fluids in the relay, bymechanical locking (also called mechanical detent because of its detenteffect) obtained by an elastic lock that deforms during the spoolmovement: or by magnetic force obtained by the action of magnets thatare placed at both ends of the spool.

Generally, these spool valve memories are provide'd with two outputs. Inthe one state or position of the relay, one of the output ports is underpressure and for proper and reliable operation of the sliding parts andfor satisfactory sealing. Additionally, their lifespan is limited andtheir cost, because of the required precision, is high.

Also known are poppet-type valve relays which allow switching by movinga poppet between two seats. The input pressures, which are to becommunicated to the output ducts, are-provided at opposite sides of thepop- I pet. The relays of this type have the advantage that they I onlyrequire very short'strokes of the poppet to effect switching, so thatvery little wear takes place. Additionally, high precision is notrequired in the construction of such relays. However, poppets are notpressure balanced, i.e., their position is affected by the action of thepressure of the fluid utilized for effecting switching, and thusdifferent locking mechanisms must be employed to retain the poppet in apreset condition. The

' locking mechanisms frequently require special elaborate designs, whichincreases the price of the relays. Fi-

nally, if two output relays are required, the use of multiple poppetsleads to complicated constructions because of the precision which isnecessitated in order to permit all the poppets to simultaneously engagetheir respective seats. Thus, while the input pressures to be switchedto the output conduits are not intended to change the state of therelay, once switching has been effected by a control pulse, theconstruction of the poppet valve relay frequently results in thesepressures undesirably changing the state of the relay.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a pneumatic memory relay which does not posses thedisadvantages of similar relays known in the prior art.

It is another object of the present invention to provide a pneumaticrelay of the type under discussion which is simple in construction andeconomical to manufacture, and which can be provided with one or twooutputs.

It is still another object of the present invention to provide a relayof the above type which is adapted to maintain a desired state, intowhich it is placed by an appropriate control pulse, subsequent to theremoval of the pulse.

It is a further object of the present invention to provide a pneumaticrelay as above described which includes magnetic locking means formaintaining the relay in a desired state.

It is a still further object of the present invention to provide apneumatic relay which can easily be modified from a single output relayto a double output relay in which the two respective outputs arecomplementary to one another.

According to the present invention, a pneumatic memory relay comprises ahousing having a space interiorily therein. First and second inputconduits are provided in said housing, said conduits respectively havingouter ends accessible exteriorly of said housing and respectively havinginner ends each communicating with said space. First and second seatmeans are respectivelyprovided at said inner ends. An output conduit insaid housing communicates with said space and with the exterior of saidhousing. Poppet means is arranged to move in said space between a firstposition in which it-sealingly engages said first seat means and placessaid output conduit in communication with said second input conduit, anda second position in which it sealingly engages said second seat meansandplaces said output conduit into communication with said first inputconduit. First and second actuating means, including means for receivingset and reset signals, are provided for moving said poppet means to saidsecond and first positions respectively, in response to application ofsaid set and reset signals. Retaining means are provided for retainingsaid poppet means in at least one of said positions, absent theapplication of the respective signal.

According to a presently preferred embodiment, said retaining meanscomprises magnetic means in the form of a permanent magnet. Said poppetmeans is in this case made from a magnetizable material such as ferrousmetal and is in the form of a flat disk, each flat surface of the diskbeing arranged to sealingly engage a different one of said seat means.

According to a further feature of the present invention, an associatedrelay means has an auxiliary output conduit and cooperates with saidmemory relay, being provided with conduit means which communicates withsaid first and second input conduits as well as with said means forreceiving said set and reset signals. Two complementary signals normallyappear at said output .seat 2 so that the pressure P does conduitsalternatively, in'response to the application of the set and resetsignals. Means are provided in the associated'relay means whichcooperate with said conduit means for generating at said auxiliaryoutput conduit an output signal which is complementary to that appearingat the first-mentioned output conduit.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING with the pneumatic memory relay toprovide two outputs which are complementary to one another.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The single output relayillustrated in FIG. 1 comprises a poppet l which is made of ferrousmetal and is in form of a flat disk. The poppet is arranged to movebetween two positions in a space 1 provided interiorly of the housing15. Seats 2 and 3 are provided at opposite sides of the space 1' and arearranged to be engaged by respective ones of the major surfaces of thepoppet 1 when the latter is in one of the two positions. The seats 2 and3 are preferably made from an elastomeric material, such as rubber,which is capable of providing a good seal when the poppet 1 comes intocontact therewith. An inlet conduit 4 provided in the housing 15 has anouter end accessible exteriorly of the housing, and an inner end whichis bounded by the seat 2 and communicates with the space 1. The conduit4 is arranged to receive a fluid under a predetermined pressure. Thepressure which is normally applied and which exists in the conduit 4 isrepresented by the reference character P. The pressure P is provided bya permanent pressure supply (not shown). In one position of the poppetl, the upper surface, as viewed in FIG. 1, engages or makes contact withthe seat 2 to thereby close or seal the inner end of the conduit 4.Magnet means, in the form of a permanent magnet 5, is provided in theregion of the seat 2 and the poppet 1 is made from a magnetizablematerial which is attracted to the magnet 5. The force of attractiondraws the poppet l in an upward direction, as viewed in FIG. 1, toinsure a good seal between the poppet l and the not appear in the relaybeyond the conduit 4.

An output conduit 15' has an inner end in communication with the space Iand an outer end which is externally accessible. The output conduit 15is provided .to communicate the'pressure conditions in the space 1 tothe exterior of the housing the thus provided output signal beingrepresented by the reference character S. A further inlet conduit 6 hasan outer end communicating with the exterior of the housing 15 and aninner end communicating with the space 1 through a seat 3 which boundsthe inner end of this conduit. With the position of the poppet 1 asshown in FIG. 1, it will be clear that the output conduit 15 is incommunication with the inlet conduit 6 through the seat 3. To improvethe fluid communication between the space 1' and the conduit 6, at leastone slot 7 is provided in a piston 8 the purpose of the piston 8 to bedescribed hereafter. I

The conduit 6 is arranged to receive a fluid at a predeterminedpressure. In accordance with the presently preferred embodiment of theinvention, the conduit 4 is supplied with a fluid at a pressure aboveatmospheric pressure, while the conduit 6 is placed at atmosphericpressure. To this end, the inlet conduit 6 extends through the housing15, and the exhaust port 6a of the conduit 6 is schematicallyillustrated as communicating with the. atmosphere.

When the poppet 1 is in the upper position so that the conduits 6 and 15communicate with each other, the memory relay is said to be in the 0"state, that is that its output S is at a relative pressure of zero.Stated another way, the 0 state of the relay indicates that the pressureS at the output or outer end of the conduit 15 is at atmosphericpressure.

Actuating means are provided which can move the poppet from the positionwherein it engages one seat, to a position where it engages the otherseat. The actuating means are adapted to bring the poppet 1 intoabutment against the seat 3, and include a'conduit 4 arranged to receivefluid under pressure, particularly to receive pneumatic pulses X,, whichwill hereinafter be referred to as set signals. When a set signal istransmitted to the conduit 4', the pneumatic control pulse is applied toone side of a diaphragm 9 which is movable in a downward direction. Uponthe application of a set signal X, the diaphragm deforms downwardly andcauses an actuating member 10, in the form of a fork or bifurcatedmember having a portion extending towards the space 1, to abut againstthe poppet l and more the same towards the seat 3.

As described above, the magnetizable poppet l is attracted by the magnet5, this attraction being effective to normally retain the poppet 1 inabutment against the seat 2. When a set signal X forces the poppet 1 tomove away from the seat 2 and towards seat 3, as described above, thepoppet l nevertheless remains under the decreased influence orattraction of the permanent magnet 5. Advantageously, the diaphragm 9 isarranged to deform sufficiently so as to cause the bifurcated actuatingmember 10 to move in a downward direction, as shown in FIG. 1, by adistance sufficient to urge the poppet 1 towards seat 3 until engagementhas been effected. Once the lower surface of the poppet 1 has come intocontact with the seat 3, the inner end of the conduit 4 is now open andcommunicates with the space 1 and, therefore, with the output conduit15. The pressure P is thereby transmitted to the output conduit 15 andthe pressure output S is equal to the pressure P. Now, however, theconduit, 6 has its inner end, bounded by the seat 3, sealed and theconduit 6 is no longer in communication with the space 1'. It willbecome evident that the pressure output S at the output conduit 15'changes from the atmospheric pressure in conduit 6 to the pressure P inconduit 4. The memory relay is then said to be in the state 1 or setposition. When the relay is in the state 1" position, it is possible toswitch the output S back, from the pressure P, to atmospheric pressureby the application of a reset signal X in conduit 6'. A pneumaticpressure applied in the conduit 6', as in the case of a pressureinconduit 4', operates on a diaphragm 11 which is arranged to deflect inthe direction of the space 1'. A piston 8 has a portion configurated topass into and extend through the seat 3, and another portion which isadjacent to the diaphragm 11. Upon deformation or flexing of thediaphragm 11, the piston 8 is urged in an upward direction, as viewed inFIG. 1, the portion extending through the seat 3 abutting against thepoppet l to urge the same to move towards the seat 2. The lifting of thepoppet I from seat 3 is facilitated by making the cross section of thediaphragm 11 as well as the cross section of the portion of the pistonengaging therewith greater than the effective cross-section of seat 3.

The poppet l, as a result of the high attractive force of the magnet 5,returns into abutment against the seat 2, atwhich time the conduit isagain placed into I communication with the conduit 6 so that the memoryrelay is again placed into the 0 state.

With the above described arrangement, the poppet 1 remains in the 0state even after the disappearance of reset signal X and only reverts tothe state l when a set signal X appears at the conduit 4'. Because ofthis characteristic, the relay is said to have a memory since it retainsits 0 state indefinitely if no external control pulses are applied toit. In order to assure the memory function, it is necessary that theforces which act on the S is the effective cross-sectional area of seat3,

S is the active area of the diaphragm 9, Sn is the active area ofdiagram 11,

F is the attraction'force developed by the magnet 5 I on the poppet lwhen-the latter abuts against the seat2,and j F is the attraction forcedeveloped by the magnet 5 on the poppet 1, when the latter abuts againstthe seat 3. Also, it will be assumed that the control signals X, and Xrepresent pressures equal to the pressure P present in conduit 4. Thefollowing relationships must then be satisfied for proper operation:

PXS F PXS F, P S P S The characteristic of a permanent magnet is suchthat the attraction forces it exerts quicklydiminish with distance ofthe magnetizable elements from the magnet.

Therefore, F will be relatively small and F which can easily beregulated by limiting the distance between the poppet and the magnet 5by means of the poppet stop 12, will be relatively high. Because all ofthese above variables may be easily modified by changing the seatcross-sectional areas, etc., the inequalities may readily be satisfiedand proper operation can reliably be obtained. This versatilitysimilarly exists for a wide range of working pressures P sufficient tomeet most applicatrons.

Push buttons 13 and 14 are manual overrides which permit changing thestates of the memory relay by simple manual control. Upon depressing ofa respective pushbutton, a force is exerted on a respective diaphragm 9or 11 which has the same effect as the forces exerted by the pressureson said diaphragms caused by the control signals X and X respectively.Thus, pushbutton 13 sets the memory to state 1 and pushbutton 14 resetsit to state 0.

According to the presently preferred embodiment, the housing 15 iscomposed of molded plastic and the holding or mounting parts 16, 1-7 and18 are press fitted in the housing. The parts 16-18 are advantageouslyprovided with annular sharp edges that achieve sealing and also firmlymaintain the parts in the housing. With such sealing means, no threadsare necessary, and the relay assumes a very compact form, which may bebuilt very economically. The present invention is not, however, limitedto this construction and other economical methods of construction canalso be used in the framework of the invention, as for example,assembling by riveting, snapping-together of elastic parts or ultrasonicwelding of plastic parts, etc.

' A particular advantage of the relay in accordance with the presentinvention, as described and illustrated with reference to FIGS. 1 and 2,is the feature of the relay which permits automatic resetting in case offailure or lackof supply pressure P. The attraction force F;, of magnet5 on poppet l is very low when the latter abuts against the seat 3.However, the force F is generally sufficient to pull the poppet 1towards the seat 2 when the pressure P equals zero, even if the poppetweight has to be overcome. This automatic reset feature in case of lackor failure of supply pressure P, is useful and, indeed, important insome automatic systems. However, in other systems it is important to usea relay that keeps its state, even when the supply pressure fails.Referring to FIG. 3, a further embodiment of the present invention meetsthe last-mentioned requirement. A second magnet 19 is provided to holdor maintain the poppet l in abutment against the seat 3, even after thesupply pressure P is removed.

' Referring to FIG. 3, the seat 3 which no longer serves to hold thepoppet l by pressure differentials applied thereacross, may have itseffective cross-sectional area reduced to a minimum so that X resetsignals, when applied to diaphragm 11, can overcome both the forcegenerated by the magnet 19 and the force generated by the pressure Papplied to the effective cross-sectional area of seat 3.

Two complementary output signals are frequently utilized in automationsystems. The memory that has just been described in conjunction withFIGS. 1-3, comprises a single output memory. Thus the single output S atthe conduit 15' is either in communication with the greater pressure Pof the conduit 4 or with the lower or atmospheric pressure of theconduit 6. These input pressures, as described above, can selectively beapplied to the output conduit 15' by the application of suitable setand-reset signals to the conduit 4 and the conduit 6 respectively.

As shown in FIG. 4, the just described memory relay may be modified byconnecting to the same a NOT relay in the form of a switch 20. Theswitch is in communication with the conduit 4 via a conduit 21. Thepressure P taken from the input conduit 4 can be selectively applied tothe output S and the output S which is the inverse of the output S. Theactual construction of the NOT relay is known and does not form part ofthe present invention. The NOTrelay 20 is adapted for connection to thememory relay as shown. Conduit means are provided in the housing,including the conduit 21 which is in communication with the conduit 4.Thus, the pressure P is simultaneously applied to the conduits 4 and 21,the latter being bounded by a seat 2' having a smallei effective crosssection. Cooperating with a diaphragm 23, the conduit 22 of the NOTrelay is in communication with the space 1. When a control signal X issupplied to the conduit 4', the control pulse is applied to thediaphragm 9. Thus, the two relays are mounted back-to-back and when thepoppet 24 is urged against the seat 2', the poppet l is urged againstthe seat 3, and vice versa. The second output of the memory relay isdesignated by reference S to indicate that it is the complement of theoutput S.

duit 6 is also applied to the diaphragm 23. On theother hand, thepressure P exerts a force on the poppet 24. The pressure differential onthe poppet 24 causes the l atter.to abut against the seat 3 and therebythe output S is essentially at the pressure P this being the supplementof the output S. In the condition illustrated in FIG. 4, the basicmemory relay is in the state since the output S of the concuit is at the0 while the auxiliary output S is in the 1 state. Accordingly, when themain relay is set, as described above, the pressure in the space I risesto the pressure P. Since conduit 22 communicates the pressure in thespace 1' to the diaphragm 23, the latter, via a piston 23', urges thepoppet towards the seat 2. In the set position of the main relay,therefore, the relay has its output at S at the 0 level.

The above described memory function, very much used in automation, hasheretofore remained difficult and costly to obtain in penumatic devicesas compared to the memory functions obtained with electrical orelectronic devices. The pneumatic memory relays with magnetic lockingachieve the object of this invention 'dependably, and the relays areeasy to construct in miniaturized form. A pneumatic relay of this typemakes the use of such relays practical in many applications where up tothis point they have been impractical.

It will be noted that during the switching from one state to another,the movement of the parts, and in particular the poppets, is reduced toa very small travel and this results in increased lifetime anddependability of the relay. Because no sliding seal is utilized the'components can operate perfectly without any lubrication. Finally, therelay does not require precautions for guiding and sealing, and can bemass produced, for example tural changes may be made without departingin any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can be applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent is:

l. A pneumatic memory relay comprising a housing having a spaceinteriorly therein: first and second input conduits in said housing,said conduits respectively having outer ends accessible exteriorly ofsaid housing and respectively having inner ends each communicating withsaid space; first and second seat means respectively provided at saidinner ends; an output conduit in said housing commincating with saidspace and with the exterior of said housing; poppet means arranged tomove in said space between a first position in which said poppet meanssealingly engages said first seat means and places said output conduitin communication with said second input conduit, and a second positionin which said poppet means sealingly engages said second seat means andplaces said output conduit into communication with said first inputconduit; first and second actuating means including means for receivingset and reset signals for moving said poppet means to said second andfirst positions, respectively, in response to application of said setand reset signals; and retaining means for retaining said poppet meansin at least one of said positions absent the application of therespective signal, wherein said retaining means comprises magneticmeans, wherein said poppet means is made from a magnetizable material,wherein said first and second seat means are spaced from each other, andwherein said first input conduit is arranged to receive fluid under apredetermined pressure, and said magnetic means is positioned in theregion of said first seat means and retains said poppet means in saidfirst position against the force applied to said poppet means by saidpredetermined pressure.

2. A pneumatic relay as defined in claim 1, wherein said first seatmeans comprises resilient means defining an opening substantially freeof obstructions.

3. The relay defined in claim 1; and further comprising means forestablishing in said first input conduit said predetermined pressure.

4. The relay defined in claim 1; and further comprising means forestablishing in said first input conduits said predeterminedpressure,and wherein said retaining means comprises means automatically operativeafter said poppet means has been moved to said first position thereoffor maintaining said poppet means in said first position even in theabsence of a reset signal and .even the absence of said predeterminedpressure, and automatically operative after said poppet means has beenmoved to said second position thereof for maintaining said poppet meansin said second position evenin the absence of a set signal and even inthe absence of said predetermined pressure.

5. A pneumatic relay as defined in claim 1, further comprising anothermagnetic means positioned in the region of said second seat means, saidmagnetic means being so selected that each magnetic means retains saidpoppet means in the position associated with the respective magneticmeans against the influence of the other magnetic means. 7

6. A pneumatic memory relay comprising a housing having a spaceinteriorly therein; first and secondinput conduits in said housing, saidconduits respectively having outer ends accessible exteriorly of saidhousing and respectively having inner ends each communicating with saidspace; first and second seat means respectively provided at said innerends; an output conduit in said housing communicating with said spaceand with the exterior of said housing; poppet means arranged to move insaid space between a first position in which said poppet means sealinglyengges said first seat means and placessaid output conduit incommunication with said second input conduit, and a second postion inwhichsaid poppet means sealingly engages said second second seat meansand places said output conduit into communication with said first inputconduit; first and second actuating means including means for receivingset and reset signals for moving said poppet means to said second andfirst positions respectively, in response to application of said set andreset signals; and retaining means for retaining said poppet means in atleast one of said positions absent the application of the respectivesignal, wherein said first and second input conduits are connected tostronger first and weaker second sources of pressure, respectively, andwherein said first and second seats, respectively, bound said inner endsof said first and second input conduits, the inner end of said secondinput conduit having a cross-sectional area greater than that of theinner end of said first input conduit.

. 7. A pneumatic relay as defined in claim 6, wherein said secondactuating means comprises movable piston means arranged to at leastpartially extend through said second seat means on the application of areset signal to thereby move said poppet means from said second to saidfirst positions.

8. The relay defined in claim 6, wherein said retaining means comprisesmeans automatically operative after said poppet means has been moved tosaid first position thereof for maintaining said poppet means in saidfirst position even in the absence of a reset signal and even in theabsence of operation of one of both of said sources of pressure, andautomatically operative after said poppet means has been moved to saidsecond position thereof for maintaining said poppet means in said secondposition even in the absence of a set signal and even in the absence'ofoperation of one or both of said sources of pressure.

' 9. A pneumatic memory relay comprising a housing having a spaceinteriorly therein; first and second input conduits in said housing,said conduits respectively having outer ends accessible exteriorly ofsaid housing cation with said second input conduit, and a secondposition in which said poppet means sealingly engages said second seatmeans and places said output conduit into communication with said firstinput conduit; first and second actuating means including means forreceiving set and reset signals for moving said poppet means to saidsecond and first positions, respectively, in response to application ofsaid set and reset signals; and retaining means for retaining saidpoppet means-in at least one of said positions absent the application ofthe respective signal, wherein said retaining means comprises magnetmeans, wherein said poppet means is made from a magnetizable material,wherein said first and second seat means are spaced from each other; andwherein said magnet means is positioned in the region of one of saidseat means and is so selected that it retains said poppet means in theposition associated with said one seat means when said first and secondinput conduits are atatmospheric pressure.

, 10. A pneumatic memory relay comprising a housing move in said spacebetween a first position in which said poppet means sealingly engagessaid first seat means and places said output conduit in communicationwith said second input conduit, and a second position in which saidpoppet means sealingly engages said second seat means and places saidoutput conduit into communication with said first input conduit; firstand second actuating means including means for receiving set and resetsignals for moving said poppet means to said second and first positions,respectively, in response to application of said set and reset signals;and retaining means for retaining said poppet means in at least one ofsaid positions absent the application of the respective signal, whereinsaid first actuating means comprises an actuating member having a firstmovable portion and at least one second portion extending towards saidspace and arranged to abut against said poppet means in response tomovement of said first portion toward said space; and diaphragm meansadjacent to said first portion and arranged to displace said actuatingmember so as to abut against said poppet means in response to receipt ofa set signal, to thereby urge said poppet means to move from said firstto said second position.

11. A pneumatic. relay as defined in claim 10, wherein said actuatingmember is substantially forkshaped.

12. A pneumatic relay as defined in claim 10, further comprising manualoverride button 'means slidably mounted on said housing and arranged toact on said diaphragm means when said button means is depressed.

13. The relay defined in claim 10, and further comprising means forestablishing in at least one of said input conduits a predeterminedpressure different from tomatically operative aftersaid poppet means hasbeen tively provided at said inner ends; an output conduit in saidhousing communicating with said space with the exterior of said housing;poppet means arranged to move in said space between a first position inwhich said poppet means sealingly engages said first seat means andplaces said output conduit in communication with said second inputconduit, and a second pos- Y tion in which said poppet means sealinglyengages said second seat means and places said output conduit intocommunication with said first input conduit; first and second actuatingmeans including means for receiving set and reset signals for movingsaid poppet means to said second and first positions, respectively, inresponse to application of said set and reset signals; and retainingmeans for retaining said poppet means in at least one of said positionsabsent the application of the respective signal, wherein said secondactuating means comprises a movable actuating member having a portionconfigurated to extend through said second seat means and arranged toabut said poppet means when the latter is in said second position; anddiaphragm means adjacent to said actuating member and arranged todisplace the latter into abutment with said poppet means in response toreceipt of a reset signal, to thereby urge said poppet means to movefrom said second to said first position.

15. A pneumatic relay as defined in claim 14, wherein aid retainingmeans comprises magnetic means positioned in the region of said firstseat means, and said poppet means is of magnetizable material, wherebysaid, poppet means is attracted towards said first seat means subsequentto being urged from said second position by said actuating member.

16. A pneumaticrelay as defined in claim 14, further comprising manualoverride button means slidably mounted on said housing and arranged toact on said diaphragm means when'said button means is depressed.

prising means for establishing in at least one of said input conduits apredetermined pressure different from I atmospheric pressure, andwherein said retaining means comprises means automatically operativeafter said poppet means has been moved to said first position thereoffor maintaining said poppet means in said first position even in theabsence of a reset signal and even in the absence of said predeterminedpressure, and automatically operative after said poppet means has beenmoved to said second position thereof for maintaining said poppet meansin said second position even in the absence of a set signal and even inthe absence of said predetermined pressure.

18. A pneumatic memory relay comprising a housing having a spaceinteriorly therein; first andsecond input conduits in said housing, saidconduits respectively having outer ends accessible exteriorly of saidhousing and respectively having inner ends each communicating with saidspace; first and second seat means respectively provided at said innerends; an output conduit in said housing communicating with said spaceand with the exterior of said housing; poppet means arranged to move insaid space between a first position in which said poppet means sealinglyengages said first seat means and places said output conduit incommication with said second input conduit, and a second postion inwhich said poppet means sealingly engages said second seat means andplaces said output conduit into communication with saidfirst inputconduit; first and second actuating means including means for receivingset and reset signals for moving said poppet means to said second andfirst positions, respectively, in response to ap plication of said setand reset signals; and retaining means for retaining said poppet meansin at least one of said positions absent the application of therespective signal, wherein one of two complementary output signalsappears at the output conduit; and further comprising-associated relaymeans cooperating with said memory relay and including conduit meanscommicating with said first and second input conduits and said means forreceiving said set and reset signals, said conduit means including another output conduit; and means cooperating with said conduit means forgenerating at said other output conduit an output signal which iscomplementary to that appearing at the first mentioned output conduit.

19. The relay defined in claim 18, and further comprising means forestablishing in at least one of said input conduits a predeterminedpressure different from atmospheric pressure, and wherein said retainingmeans comprises means automatically operative after said poppet meanshas been moved to said first position thereof for maintaining saidpoppet means in said first position even in the absence of a resetsignal and even in the absence of said predetermined pressure, andautomatically operative after said poppet means has been moved to saidsecond position thereof for maintaining said poppet means in said secondposition even in the absence of-a set signal and even in the absence ofsaid predetermined pressure. v

20. A pneumatic memory relay comprising a housing having a spaceinteriorly therein; first and second input conduits in said housing,said conduits respectively having outer ends accessible exteriorly ofsaid housing and respectively having inner ,ends each communicating withsaid space; first and second seat means respectively provided at saidinner ends; an output conduit in said housing communicating with saidspace and with the exterior of said housing; poppet means arranged tomove in said space between a-first position in which said poppet meanssealingly engages said first seat means and places said output conduitin communication with said second input conduit, and a second positionin which said poppet means sealingly engages said second seat means andplaces said output conduit into communication with said first inputconduit; first and second actuating means including means for receivingset and reset signals for moving said poppet means to said second andfirst positions, respectively, in response to application of said setand reset signals; means for establishing in at least a predeterminedone of said input conduits a predetermined pressure which when saidpoppet means is in the position thereof sealingly engaging the seatmeans associated with said predetermined one of said input conduitsexerts a pushing force upon said poppet means in a direction tending tomove said poppet means to the other position thereof; and retainingmeans for retaining said poppet means in at least said predeterminedposition absent the application of the respective one of said set andreset signals.

21. The relay defined in claim 20, wherein saidretaining means comprisesmeans automatically operative after said poppet means has been moved tosaid first position thereof for holding said poppet means in said firstposition even in the absence of a reset signal and even in the absenceof said predetermined pressure, and automatically operative after saidpoppet means has been moved to said second position thereof for holdingsaid poppet means in said second position even in the absence of a setsignal and even in the absence of said predetermined pressure.

22. A pneumatic memory relay comprising a housing having a spaceinteriorly therein; first and second input conduits in said housing,said conduits respectively having outer ends accessible exteriorly ofsaid housing and respectively having inner ends each communicating withsaid space; first and second seat means respectively provided at saidinner ends; an output conduit in said housing communicating with saidspace and with the exterior of said housing; magnetically attractablepoppet means arranged to move in said space between a first position inwhich said poppet means sealingly engages said first seat means andplaces said output conduit in communication with said second inputconduit, and a second'position in which said poppet means sealinglyengages said second seat means and places said output conduit intocommunication with said input conduit; first and second actuating meansincluding means for receiving set and reset signals for moving saidpoppet means to said second and first positions, respectively, inresponse to application of said set and reset signals; and magneticretaining means operative after said poppet means has been moved to saidfirst position thereof for holding said poppet means in said firstposition even in the absence of a reset signal by applying to saidpoppet means a magnetic attracting force holding said poppet means insaid first position, and operative after said poppet means has beenmoved to said second position thereof for holding said poppet means insaid second position even in the absence of a set signal by applying tosaid poppet means a magnetic attracting force holding said poppet meansin said second position.

23. A relay defined in claim 22, further including means forestablishing in at least one of said conduits a predetermined fluidpressure, and wherein said magnetic retaining means comprises meansoperative after said poppet means has been moved to said first positionthereof for holding said poppet means in said first position even in theabsence of a reset signal and even in the absence of said predeterminedpressure by applying to said poppet means a magnetic attracting forceholding said poppet means in said first position, and operative aftersaid poppet means has been moved to said second position thereof forholding said poppet means in said second position even in the absence ofa set signal and even in the absence of said predetermined pressure byapplying to said poppet means a magnetic attracting force holding saidpoppet means in said second position.

1. A pneumatic memory relay comprising a housing having a spaceinteriorly therein: first and second input conduits in said housing,said conduits respectively having outer ends accessible exteriorly ofsaid housing and respectively having inner ends each communicating withsaid space; first and second seat means respectively provided at saidinner ends; an output conduit in said housing communicating with saidspace and with the exterior of said housing; poppet means arranged tomove in said space between a first position in which said poppet meanssealingly engages said first seat means and places said output conduitin communication with said second input conduit, and a second positionin which said poppet means sealingly engages said second seat means andplaces said output conduit into communication with said first inputconduit; first and second actuating means including means for receivingset and reset signals for moving said poppet means to said second andfirst positions, respectively, in response to application of said setand reset signals; and retaining means for retaining said poppet meansin at least one of said positions absent the application of therespective signal, wherein said retaining means comprises magneticmeans, wherein said poppet means is made from a magnetizable material,wherein said first and second seat means are spaced from each other, andwherein said first input conduit is arranged to receive fluid under apredetermined pressure, and said magnetic means is positioned in theregion of said first seat means and retains said poppet means in saidfirst position against the force applied to said poppet means by saidpredetermined pressure.
 2. A pneumatic relay as defined in claim 1,wherein said first seat means comprises resilient means defining anopening substantially free of obstructions.
 3. The relay defined inclaim 1; and further comprising means for establishing in said firstinput conduit said predetermined pressure.
 4. The relay defined in claim1; and further comprising means for establishing in said first inputconduits said predetermined pressure, and wherein said retaining meanscomprises means automatically operative after said poppet means has beenmoved to said first position thereof for maintaining said poppet meansin said first position even in the absence of a reset signal and eventhe absence of said predetermined pressure, and automatically operativeafter said poppet means has been moved to said second position thereoffor maintaining said poppet means in said second position even in theabsence of a set signal and even in the absence of said predeterminedpressure.
 5. A pneumatic relay as defined in claim 1, further comprisinganother magnetic means positioned in the region of said second seatmeans, said magnetic means being so selected that each magnetic meansretains said poppet means in the position associated with the respectivemagnetic means against the influence of the other magnetic means.
 6. Apneumatic memory relay comprising a housing having a space interiorlytherein; first and second input conduits in said housing, said conduitsrespectively having outer ends accessible exteriorly of said housing andrespectively having inner ends each communicating with said space; firstand second seat means respectively provided at said inner ends; anoutput conduit in said housing communicating with said space and withthe exterior of said housing; poppet means arranged to move in saidspace between a first position in which said poppet means sealinglyengages said first seat means and places said output conduit incommunication with said second input conduit, and a second position inwhich said poppet means sealingly engages said second second seat meansand places said output conduit into communication with said first inputconduit; first and second actuating means including means for receivingset and reset signals for moving said poppet means to said second andfirst positions respectively, in response to application of said set andreset signals; and retaining means for retaining said poppet means in atleast one of said positions absent the application of the respectivesignal, wherein said first and second input conduits are connected tostronger first and weaker second sources of pressure, respectively, andwherein said first and second seats, respectively, bound said inner endsof said first and second input conduits, the inner end of said secondinput conduit having a cross-sectional area greater than that of theinner end of said first input conduit.
 7. A pneumatic relay as definedin claim 6, wherein said second actuating means comprises movable pistonmeans arranged to at least partially extend through said second seatmeans on the application of a reset signal to thereby move said poppetmeans from said second to said first positions.
 8. The relay defined inclaim 6, wherein said retaining means comprises means automaticallyoperative after said poppet means has been moved to said first positionthereof for maintaining said poppet means in said first position even inthe absence of a reset signal and even in the absence of operation ofone of both of said sources of pressure, and automatically operativeafter said poppet means has been moved to said second position thereoffor maintaining said poppet means in said second position even in theabsence of a set signal and even in the absence of operation of one orboth of said sources of pressure.
 9. A pneumatic memory relay comprisinga housing having a space interiorly therein; first and second inputconduits in said housing, said conduits respectively having outer endsaccessible exteriorly of said housing and respectively having inner endseach communicating with said space; first and second seat meansrespectively provided at said inner ends; and output conduit in saidhousing communicating with said space and with the exterior of saidhousing; poppet means arranged to move in said space between a firstposition in which said poppet means sealingly engages said first seatmeans and places said output conduit in communication with said secondinput conduit, and a second position in which said poppet meanssealingly engages said second seat means and places said output conduitinto communication with said first input conduit; first and secondactuating means including means for receiving set and reset signals formoving said poppet means to said second and first positions,respectively, in response to application of said set and reset signals;and retaining means for retaining said poppet means in at least one ofsaid positions absent the application of the respective signal, whereinsaid retaining means comprises magnet means, wherein said poppet meansis made from a magnetizable material, wherein said first and second seatmeans are spaced from each other; and wherein said magnet means ispositioned in the region of one of said seat means and is so selectedthat it retains said poppet means in the position associated with saidone seat means when said first and second input conduits are atatmospheric pressure.
 10. A pneumatic memory relay comprising a housinghaving a space interiorly therein; first and second input conduits insaid housing, said conduits respectively having outer ends accessibleexteriorly of said housing and respectively having inner ends eachcommunicating with said space; first and second seat means respectivelyprovided at said inner ends; an output conduit in said housingcommunicating with said space and with the exterior of said housing;poppet means arranged to move in said space between a first position inwhich said poppet means sealingly engages said first seat means andplaces said output conduit in communication with said second inputconduit, and a second position in which said poppet means sealinglyengages said second seat means and places said output conduit intocommunication with said first input conduit; first and second actuatingmeans including means for receiving set and reset signals for movingsaid poppet means to said second and first positions, respectively, inresponse to application of said set and reset signals; and retainingmeans for retaining said poppet means in at least one of said positionsabsent the application of the respective signal, wherein said firstactuating means comprises an actuating member having a first movableportion and at least one second portion extending towards said space andarranged to abut against said poppet means in response to movement ofsaid first portion toward said space; and diaphragm means adjacent tosaid first portion and arranged to displace said actuating member so asto abut against said poppet means in response to receipt of a setsignal, to thereby urge said poppet means to move from said first tosaid second position.
 11. A pneumatic relay as defined in claim 10,wherein said actuating member is substantially fork-shaped.
 12. Apneumatic relay as defined in claim 10, further comprising manualoverride button means slidably mounted on said housing and arranged toact on said diaphragm means when said button means is depressed.
 13. Therelay defined in claim 10, and further comprising means for establishingin at least one of said input conduits a predetermined pressuredifferent from atmospheric pressure, and wherein said retaining meanscomprises means automatically operative after said poppet means has beenmoved to said first position thereof for maintaining said poppet meansin said first position even in the absence of a reset signal and even inthe absence of said predetermined pressure, and automatically operativeafter said poppet means has been moved to said second position thereoffor maintaining said poppet means in said second position even in theabsence of a set signal and even in the absence of said predeterminedpressure.
 14. A pneumatic memory relay comprising a housing having aspace interiorly therein; first and second input conduits in saidhousing, said conduits respectively having outer ends accessibleexteriorly of said housing and respectively having inner ends eachcommunicating with said space; first and second seat means respectivelyprovided at said inner ends; an output conduit in said housingcommunicating with said space and with the exterior of said housing;poppet means arranged to move in said space between a first position inwhich said poppet means sealingly engages said first seat means andplaces said output conduit in communication with said second inputconduit, and a second position in which said poppet means sealinglyengages said second seat means and places said output conduit intocommunication with said first input conduit; first and second actuatingmeans including means for receiving set and reset signals for movingsaid poppet means to said second and first positions, respectively, inresponse to application of said set and reset signals; and retainingmeans for retaining said poppet means in at least one of said positionsabsent the application of the respective signal, wherein said secondactuating means comprises a movable actuating member having a portionconfigurated to extend through said second seat means and arranged toabut said poppet means when the latter is in said second position; anddiaphragm means adjacent to said actuating member and arranged todisplace the latter into abutment with said poppet means in response toreceipt of a reset signal, to thereby urge said poppet means to movefrom said second to said first position.
 15. A pneumatic relay asdefined in claim 14, wherein said retaining means comprises magneticmeans positioned in the region of said first seat means, and said poppetmeans is of magnetizable material, whereby said poppet means isattracted towards said first seat means subsequent to being urged fromsaid second position by said actuating member.
 16. A pneumatic relay asdefined in claim 14, further comprising manual override button meansslidably mounted on said housing and arranged to act on said diaphragmmeans when said button means is depressed.
 17. The relay defined inclaim 14, and further comprising means for establishing in at least oneof said input conduits a predetermined pressure different fromatmospheric pressure, and wherein said retaining means comprises meansautomatically operative after said poppet means has been moved to saidfirst position thereof for maintaining said poppet means in said firstposition even in the absence of a reset signal and even in the absenceof said predetermined pressure, and automatically operative after saidpoppet means has been moved to said second position thereof formaintaining said poppet means in said second position even in theabsence of a set signal and even in the absence of said predeterminedpressure.
 18. A pneumatic memory relay comprising a housing having aspace interiorly therein; first and second input conduits in saidhousing, said conduits respectively having outer ends accessibleexteriorly of said housing and respectively having inner ends eachcommunicating with said space; first and second seat means respectivelyprovided at said inner ends; an output conduit in said housingcommunicating with said space and with the exterior of said housing;poppet means arranged to move in said space between a first position inwhich said poppet means sealingly engages said first seat means andplaces said output conduit in communication with said second inputconduit, and a secoNd position in which said poppet means sealinglyengages said second seat means and places said output conduit intocommunication with said first input conduit; first and second actuatingmeans including means for receiving set and reset signals for movingsaid poppet means to said second and first positions, respectively, inresponse to application of said set and reset signals; and retainingmeans for retaining said poppet means in at least one of said positionsabsent the application of the respective signal, wherein one of twocomplementary output signals appears at the output conduit; and furthercomprising associated relay means cooperating with said memory relay andincluding conduit means communicating with said first and second inputconduits and said means for receiving said set and reset signals, saidconduit means including an other output conduit; and means cooperatingwith said conduit means for generating at said other output conduit anoutput signal which is complementary to that appearing at the firstmentioned output conduit.
 19. The relay defined in claim 18, and furthercomprising means for establishing in at least one of said input conduitsa predetermined pressure different from atmospheric pressure, andwherein said retaining means comprises means automatically operativeafter said poppet means has been moved to said first position thereoffor maintaining said poppet means in said first position even in theabsence of a reset signal and even in the absence of said predeterminedpressure, and automatically operative after said poppet means has beenmoved to said second position thereof for maintaining said poppet meansin said second position even in the absence of a set signal and even inthe absence of said predetermined pressure.
 20. A pneumatic memory relaycomprising a housing having a space interiorly therein; first and secondinput conduits in said housing, said conduits respectively having outerends accessible exteriorly of said housing and respectively having innerends each communicating with said space; first and second seat meansrespectively provided at said inner ends; an output conduit in saidhousing communicating with said space and with the exterior of saidhousing; poppet means arranged to move in said space between a firstposition in which said poppet means sealingly engages said first seatmeans and places said output conduit in communication with said secondinput conduit, and a second position in which said poppet meanssealingly engages said second seat means and places said output conduitinto communication with said first input conduit; first and secondactuating means including means for receiving set and reset signals formoving said poppet means to said second and first positions,respectively, in response to application of said set and reset signals;means for establishing in at least a predetermined one of said inputconduits a predetermined pressure which when said poppet means is in theposition thereof sealingly engaging the seat means associated with saidpredetermined one of said input conduits exerts a pushing force uponsaid poppet means in a direction tending to move said poppet means tothe other position thereof; and retaining means for retaining saidpoppet means in at least said predetermined position absent theapplication of the respective one of said set and reset signals.
 21. Therelay defined in claim 20, wherein said retaining means comprises meansautomatically operative after said poppet means has been moved to saidfirst position thereof for holding said poppet means in said firstposition even in the absence of a reset signal and even in the absenceof said predetermined pressure, and automatically operative after saidpoppet means has been moved to said second position thereof for holdingsaid poppet means in said second position even in the absence of a setsignal and even in the absence of said predetermined pressure.
 22. Apneumatic memory relay comprising a housing having a space inTeriorlytherein; first and second input conduits in said housing, said conduitsrespectively having outer ends accessible exteriorly of said housing andrespectively having inner ends each communicating with said space; firstand second seat means respectively provided at said inner ends; anoutput conduit in said housing communicating with said space and withthe exterior of said housing; magnetically attractable poppet meansarranged to move in said space between a first position in which saidpoppet means sealingly engages said first seat means and places saidoutput conduit in communication with said second input conduit, and asecond position in which said poppet means sealingly engages said secondseat means and places said output conduit into communication with saidfirst input conduit; first and second actuating means including meansfor receiving set and reset signals for moving said poppet means to saidsecond and first positions, respectively, in response to application ofsaid set and reset signals; and magnetic retaining means operative aftersaid poppet means has been moved to said first position thereof forholding said poppet means in said first position even in the absence ofa reset signal by applying to said poppet means a magnetic attractingforce holding said poppet means in said first position, and operativeafter said poppet means has been moved to said second position thereoffor holding said poppet means in said second position even in theabsence of a set signal by applying to said poppet means a magneticattracting force holding said poppet means in said second position. 23.A relay defined in claim 22, further including means for establishing inat least one of said conduits a predetermined fluid pressure, andwherein said magnetic retaining means comprises means operative aftersaid poppet means has been moved to said first position thereof forholding said poppet means in said first position even in the absence ofa reset signal and even in the absence of said predetermined pressure byapplying to said poppet means a magnetic attracting force holding saidpoppet means in said first position, and operative after said poppetmeans has been moved to said second position thereof for holding saidpoppet means in said second position even in the absence of a set signaland even in the absence of said predetermined pressure by applying tosaid poppet means a magnetic attracting force holding said poppet meansin said second position.